When I converted the module to Drupal 7, I tried to repeat the same schema to perform the block settings validation I followed in Drupal 6, but it does not work.
I posted the question in the "Module Development and Code Questions": http://drupal.org/node/1314552 but I got no answer (it has been there for one month). Further details can be found there.
If anyone knows what the best practices to perform the validation of the block configuration settings in D7 are, it would be great if it would be added it there, so it is add it to this module and it can be reached by some other people with the same question (I was researching and I could not find the same question anywhere else).